This invention relates to domical enclosures assembled from polygonal panels which interact to form a substantially self-supporting integral structure.
It is well known that domical buildings enclose a greater volume of space than conventional rectangular structures for an equivalent amount of structural material. Domes also possess a very high strength-to-weight ratio, and high stability because a force applied at any point is resisted throughout the structure.
However, domical structures have not gained wide acceptance in spite of these significant advantages. One of the reasons for this lack of acceptance is the difficulty encountered heretofore in erecting such structures. Most domical structures utilize components which are not easily assembled in the field. Further difficulties have been encountered in causing the dome structure to be sufficiently integral and continuous so as to have a water-tight outer surface acceptable as a roof for outdoor utilization.
Spherically configured dome structures which can be fabricated by the assembly of polygonal panels have been disclosed in numerous references. For example, U.S. Pat. Nos. 2,682,235; 3,197,927 and others to R. Fuller disclose the fabrication of geodesic structures based upon the icosahedron and other geometrical forms that define an enclosed volume. In such geodesic structures, a series of polygonal panels is arranged in continuous abutting relationship such that all vertices are located within a spherical locus. The polygons may be curved, in which case a spherical outer surface is formed, or flat, in which case the resultant outer surface of the structure is faceted or pyramidal. In order to permit use as a dwelling, the structure must be rendered water-impermeable and provided with thermal insulation. Such features are generally found difficult to achieve.
In using flat polygonal panels to construct a volume-enclosing geometric form having a center of symmetry, the greater the number of panels required to complete the form, the closer the outer appearance approaches a spherical shape. This concept may be visualized by contemplation of the series of platonic polyhedrons: tetrahedron, cube, octahedron, dodecahedron and icosahedron, each polyhedron being comprised of an even number of identical flat polygons in abutting juxtaposition wherein the abutment vertices are disposed within a spherical locus, and the center of each polygon is equidistantly spaced from the center of said sphere. As the number of polygons required to complete the volume-enclosing polyhedral surfaces increases, the outward appearance approaches spherical.
A particularly significant manner of approaching sphericity via a multifaceted surface involves the use of an icosahedron wherein each of its twenty triangular faces is further subdivided so as to be comprised of a plurality of smaller triangles, the vertices of which lie within the same spherical locus as the three vertices of the original triangle. The first stage of such subdivision is referred to as a two-frequency icosahedron, and is produced by causing each side of the original triangles to be divided in half, thereby forming four smaller triangles and producing a total surface comprised of eighty triangles. In analogous manner, the icosahedron may be further modified in even higher frequency subdivisions to produce surfaces approaching sphericity comprised of great numbers of relatively small, flat triangular faces.
It has been disclosed in U.S. Pat. Nos. 4,092,810; 3,881,284 and elsewhere that, in assembling panels to form a self-supporting dome having no strengthening or supporting means supplementing said panels, the edges of said panels may have an abutment surface or shoulder enabling adjacent panels to be interconnected at their common edges. Bolts adapted to pass through holes in said shoulders have been disclosed as the preferred fastening means.
U.S. Pat. No. 2,958,918 describes connecting means in the form of paired projections and recesses associated with the edges of building block segments to facilitate their assembly as a domed structure.
The above-mentioned joining techniques, where applied to the fabrication of domed structures from panels, are slow because of difficulties in securing alignment of localized paired fittings or holes. In still further known methods for joining panels, problems that have been encountered include inadequate joint strength, joints that are difficult to render water-tight, requirement of a large number of dissimilar panels, and systems of high cost.
Because of the critical interfitting of panels necessary in fabricating a domed structure, proper placement of the initial panels is important, whether the dome is constructed upwardly from its base or downwardly from its top while suspended by an overhead crane or other temporary means.
The terms "domed" or "domical" as used herein are intended to designate domes, spheres, spherical segments or truncations thereof, and structures of generally rounded appearances whether having a smooth or multifaceted outer contour.
It is an object of the present invention to provide a domed structure which can be easily assembled from a plurality of substantially flat polygonal panels.
Another object of this invention is to provide a domed structure of the aforesaid nature comprised of a small number of dissimilar panels.
A further object of this invention is to provide a domed structure of the aforesaid nature possessing sufficient strength, water-imperviousness and thermal barrier characteristics to be useful as an inhabitable outdoor building.
A still further object of this invention is to provide a domed structure of the aforesaid nature which is improved with respect to ease of construction upwardly from its base.
These objects and other objects and advantages of the invention will be apparent from the following description.